April 2012 Climate and Hydrology Summary

April 2012

Tulsa: April 2012 was the 10th warmest (65.6°F; since 1905) and the 59th driest (3.62", tied with 1910; since 1888) April on record.

The last 28°F or colder low temperature in Tulsa during this past cold season occurred on February 12, 2012 (with a low of 16°F). This is the record earliest date of the last hard spring freeze in Tulsa (since records began in 1906). The previous record was February 14, which occurred in 1981. Tulsa was only 4 days away from the record earliest date of the last spring freeze. The current record for the earliest last freeze is March 6.

Tulsa: The Winter 2011-12 seasonal snowfall total is 1.7", making this the 10th least snowiest cold season on record (since records began 1900-01). This follows the snowiest cold season on record in 2010-11!

Fort Smith: April 2012 was the 3rd warmest (67.5°F; since 1883) and the 48th driest (2.99"; since 1883) April on record.

Rainfall totals for April 2012 ranged from near 12” along the Oklahoma-Kansas border to near 1” in southeast Oklahoma. Areas northwest of I-44 received above normal rainfall for April, with locations near the Oklahoma-Kansas border getting 200-350% of the normal April rain. For most of the remainder of eastern OK and northwest AR, this month’s rainfall was only 25% to 75% of normal.

A heavy rain, flood, and severe weather event affected northeast OK April 29-May 1. After 3 days of thunderstorms, most locations northwest of I-44 received a total of 2” to 10” of rain. All of this rain led to widespread damage, especially to many roads and several homes, across northeast OK. Thankfully, no fatalities were reported, thanks in part to the efforts of swift water rescue teams. In addition to the flooding, 4 confirmed tornadoes (and 4 possible tornadoes pending at the time of this writing) also occurred.

Two river forecast points exceeded moderate flood stage this month, and one other river forecast point reached minor flood stage. See the detailed report for more information.

According to the Drought Monitor from May 1, 2012 (Figs 2, 3), drought conditions no longer existed in eastern OK and northwest AR.

According to the Oklahoma Climatological Survey (OCS) for April 2012, northeast OK ranked as the 17th wettest, east central OK ranked as the 20th driest, and southeast OK ranked as the 13th driest April since records began in 1921.

Outlook

The Climate Prediction Center CPC outlook for May 2012 (issued April 30, 2012) indicates an enhanced chance for above normal temperatures and equal chances for above, near, and below median precipitation for the entire area. This outlook was based primarily on short-term dynamic computer models.

For the 3-month period May-June-July 2012, CPC is forecasting a slightly enhanced chance for above average temperatures across southeast OK and west central AR, with equal chances for above, near, and below normal temperatures elsewhere. This outlook also indicates equal chances for above, near, and below median precipitation across the region (outlook issued April 19, 2012). This outlook is based primarily on dynamic computer models since La Niña no longer plays a direct role in the forecast.

According to CPC, La Niña has weakened and ENSO neutral conditions are expected through the summer. However, there may be some lingering atmospheric and soil moisture impacts from La Niña in the short-term.